1. Field of the Invention
The present invention relates to a device for feeding sheets one by one, of a type wherein an uppermost sheet of stacked sheets to be fed is held by conveying systems disposed around a rotatable drum and the sheet thus held is then reversed, thereby enabling the sheet to be delivered to another station.
2. Description of the Related Art
In order to withdraw sheets such as photographic light-sensitive mediums (e.g., a X-ray film, graphic art films etc.), one by one, from a supply magazine in which the sheets have been accommodated, so as to enable delivery of the sheets to succeeding stations (e.g., an exposure station, a development station, etc.), there is employed in a sheet feeding device, a suction cup or pad to be incorporated therein, which is coupled to a vacuum source. There is often a situation in which, for example, the uppermost sheet which has been attracted and held by the suction pad under suction, must temporarily be placed in a waiting state in the course of delivery along the path of the sheet feeding device, without being delivered directly to an automatic photographic processor, according to the purpose of its use.
Since suction tends to damage the surfaces of the sheets being fed, these sheets are accommodated in the supply magazine in a stacked state in such a manner that these surface coated with sensitive material of the sheets are usually directed downwards. There is therefore often a situation in which the surface of each of the sheets thus stacked must be turned over during transportation of the sheet in accordance with the type of the device.
FIG. 1 shows a conventional reversal mechanism for turning the sheet over. The reversal mechanism comprises a triangle-shaped guide 2 disposed in the course of transportation path of a sheet feeding device 1, pairs of rollers 3a, 3c disposed on both sides of the guide 2, pairs of rollers 3b, 3d disposed above the guide 2, and standby port 4 and a guide plate 5 both located above the guide 2.
The reversal mechanism is activated in the following manner. A sheet e.g., a photographic film F, having a surface coated with a sensitive material facing downwards, is attracted under suction by a suction cup or pad 6 so as to be fed toward the guide 2 and transported upwards along one of slanted surfaces of the guide 2. Thereafter, the photographic film F is transported to the standby port 4 so as to be held between the paired rollers 3d. Then, the guide 2 is moved toward the left side as viewed in FIG. 1, and the leading end of the photographic film F, which has been held by the rollers 3d, is moved along the other of the slanted surfaces of the guide 2, followed by the transportation of the film F toward an automatic photographic processor as a next step via a conveying system 8 including drums or the like, whereby the light-sensitive layer of the sheet can be oriented upwards, thereby reversal operation by the reversal mechanism is completed.
In the sheet feeding device 1, however, the photographic film F must temporarily be held at the standby port 4 disposed in the transportation path of the film F. Thus, when a photographic film having large dimension is used, the space of the standby port 4 for receiving this photographic film therein becomes large to meet the size of the film F, so that the sheet feeding device 1 itself also becomes larger in size. When sheets having inferior quality or shape, e.g., curled sheets, are used, the curled portions of the sheets abut against the rollers 3b near the standby port 4 disposed above the guide 2, so that the sheets cannot be introduced into the standby port 4.